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From |
Tim Scharks <tim.scharks@gmail.com> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: Average of Sample vesus Sub-Samples |

Date |
Fri, 19 Mar 2010 09:05:49 -0700 |

Ah, I see That's what I get for faulty inference and reading too fast...thanks! On Fri, Mar 19, 2010 at 8:59 AM, Jeph Herrin <junk@spandrel.net> wrote: > The original question was not whether these two > numbers could differ, but whether the average of the > larger group could be greater than the mean of the > two sub averages. In your case they differ, but the > average of the larger group is smaller. > > I think you have to have negative numbers to reverse > the inequality. > > cheers, > Jeph > > > Tim Scharks wrote: >> >> but what about >> >> A = 1, 1, 1 >> B = 3 >> m(A) = 1 >> m(B) = 3 >> (m(A)+m(B))/2=2 >> mean (A+B) =1.5 >> >> uh oh... >> >> The problem is not negative numbers--it is your failure to weight the >> subsample means according to their relative size: >> >> (m(A)*3+m(B)*1)/4 =1.5 >> m(A+B) = 1.5 >> >> >> On Fri, Mar 19, 2010 at 6:49 AM, Jeph Herrin <junk@spandrel.net> wrote: >>> >>> Yes, if they are negative. >>> >>> >>> A = -1,-1,-1 >>> B = -3 >>> then >>> mean(A) = -1 >>> mean(B) = -3 >>> (mean(A)+mean(B))/2 = -2 >>> mean(A+B)= -6/4 = -1.5 >>> >>> -1.5 > -2 >>> >>> So the average of all 4 numbers is larger than >>> the average of the means of the two subsamples. >>> >>> >>> hth, >>> Jeph >>> >>> >>> >>> >>> >>> Erasmo Giambona wrote: >>>> >>>> Dear Statalisters, >>>> >>>> Is it possible that the arithmetic average of a sample is larger than >>>> the averages of two sub-samples containing overall all the >>>> observations of the full samples? >>>> >>>> Any thoughts would be appreciated, >>>> >>>> Erasmo >>>> * >>>> * For searches and help try: >>>> * http://www.stata.com/help.cgi?search >>>> * http://www.stata.com/support/statalist/faq >>>> * http://www.ats.ucla.edu/stat/stata/ >>>> >>> * >>> * For searches and help try: >>> * http://www.stata.com/help.cgi?search >>> * http://www.stata.com/support/statalist/faq >>> * http://www.ats.ucla.edu/stat/stata/ >>> >> >> * >> * For searches and help try: >> * http://www.stata.com/help.cgi?search >> * http://www.stata.com/support/statalist/faq >> * http://www.ats.ucla.edu/stat/stata/ >> > * > * For searches and help try: > * http://www.stata.com/help.cgi?search > * http://www.stata.com/support/statalist/faq > * http://www.ats.ucla.edu/stat/stata/ > * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/

**Follow-Ups**:**Re: st: Average of Sample vesus Sub-Samples***From:*Erasmo Giambona <e.giambona@gmail.com>

**References**:**st: Average of Sample vesus Sub-Samples***From:*Erasmo Giambona <e.giambona@gmail.com>

**Re: st: Average of Sample vesus Sub-Samples***From:*Jeph Herrin <junk@spandrel.net>

**Re: st: Average of Sample vesus Sub-Samples***From:*Tim Scharks <tim.scharks@gmail.com>

**Re: st: Average of Sample vesus Sub-Samples***From:*Jeph Herrin <junk@spandrel.net>

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